|Publication number||US5124672 A|
|Application number||US 07/382,557|
|Publication date||Jun 23, 1992|
|Filing date||Jul 19, 1989|
|Priority date||Aug 16, 1988|
|Publication number||07382557, 382557, US 5124672 A, US 5124672A, US-A-5124672, US5124672 A, US5124672A|
|Inventors||Erkki J. Kuisma|
|Original Assignee||Nokia-Mobira Oy|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (1), Referenced by (31), Classifications (9), Legal Events (4)|
|External Links: USPTO, USPTO Assignment, Espacenet|
The invention relates to a circuit arrangement in which a radio transmission frequency is modulated by means of a baseband signal.
In order to generate digital modulation (FSK, PSK, QAM, etc.) the so-called I, Q or quadrature principle is typically applied, in which the sin and cos wave shapes of the carrier wave are multiplied by the sin and cos wave shapes of the modulating signal, after which the results are summed.
Analog frequency modulation is typically created by controlling, by means of a voltage corresponding to the modulating signal, a voltage-controlled oscillator generating the carrier wave frequency. Another method of generating analog frequency modulation is based on the I, Q principle, as is the digital modulation. The quadrature I, Q signal shapes are then formed from an analog reception signal. The generation of I, Q signal shapes is known e.g. from the FI patent application 843 826.
In applications using both digital and analog transmission channels (for instance the future US digital mobile phone system) it is advantageous that the same equipment be able to generate both the digital modulation and the analog modulation to be used.
According to the invention, in order to solve the problem of digital and analog modulation, a circuit has been set up in which a radio frequency signal is modulated by either an analog or digital baseband signal. The digital or analog signal is shaped by an I,Q generator into I,Q wave shapes. These shapes are coupled to the high frequency stage of a transmitter, optionally via an intermediate frequency stage.
The sole FIGURE illustrates a circuit for either analog or digital modulation according to the present invention, but with the required amplifiers, filters, etc. not being shown.
The illustrated circuit set-up contains the I, Q generators 1 and 2 for analog as well as digital modulation. The desired modulation is selected by means of the couplers (K1, K2).
In the position d of the couplers K1 and K2 digital (DIG) frequency modulation is selected, i.e. signals ID, QD are formed where.
ID =sin φ(t)
QD =cos φ(t)
In the formulas, φ (t) is the signal shape characteristic for each modulation method, corresponding to a reception bit or bit combination.
In the position a of the couplers K1 and K2, analog (ANAL) frequency modulation is selected, i.e. the signals IA, QA are formed. In this modulation process the modulating signal is the time derivative dx/dt of the signal x (t).
By means of the I, Q generator 2 the signals IA, QA are formed, for which the following equation is valid:
IA =sin (k·x(t))
QA =cos (k·x(t))
The equipment may include an intermediate frequency f1, with which the selected signals I, Q are first mixed in the intermediate frequency stage 3, as shown in the FIGURE. The I, Q signal can optionally be mixed or heterodyned directly to the final frequency fc. Oscillators for creating the sin and cos signal shapes of these frequency are thus needed. The mixing results of the intermediate frequency stage 3 are summed and the resulting signal is conducted to stage 4 where it is mixed with the transmit frequency fc.
This results in a signal U which is modulated to the transmission frequency according to the formula:
U=sin (ωc ·t+φ(t) with digital modulation
U=sin (ωc ·t+k·x(t) with analog modulation
The circuits 1, 2, 3 and 4 are not described in detail in this connection, since they are obvious to a person skilled in the art on the basis of the figure.
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|U.S. Classification||332/103, 455/74, 332/119, 455/93|
|International Classification||H04L27/12, H03C3/00, H03C1/00|
|Jul 19, 1989||AS||Assignment|
Owner name: NOKIA-MOBIRA OY, SALO, FINLAND A CORP. OF FINLAND
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:KUISMA, ERKKI J.;REEL/FRAME:005107/0864
Effective date: 19890622
|Sep 26, 1995||FPAY||Fee payment|
Year of fee payment: 4
|Dec 13, 1999||FPAY||Fee payment|
Year of fee payment: 8
|Nov 26, 2003||FPAY||Fee payment|
Year of fee payment: 12